Digital pan-tilt cameras, hereinafter referred to as PT cameras, are often used in monitoring and surveillance applications and are therefore often required to capture images with high quality. The quality of the captured images from cameras becomes even more important when the cameras becomes more intelligent and therefore relies even more on that the quality of the images captured for processing in the camera is high.
There are quite many factors that have effect on the quality of an image captured by a digital camera. For example is the lighting of the scene to capture one such factor, less light results in less quality. Other factors are the quality of the lenses and the resolution of the image sensor. Yet another factor is noise from the image sensor of the digital camera. Even when using a High Definition (HD) image sensor having high resolution the acquired image may gain much quality from noise reduction.
In a modern CMOS based image sensor the light from the scene to capture is collected and transformed into an analog electrical signal. This analog electrical signal is converted into a digital signal by an on chip analog to digital converter. The alternative technology used to capture images is CCD image sensors. These CCD image sensors usually require a couple of external components in order to reach the same functionality as the CMOS image sensor. These components should be arranged physically close to the sensor in order not to degrade the image signal with noise. Moreover, an increased temperature of a CMOS sensor or a CCD sensor makes the images from the image sensor noisier. In order to reduce the noise of the captured images various noise reduction techniques are applied both to the analog signal and to the digital signal. In some critical installations the image sensor may even be cooled using a cooling system external to the image sensor.